Mechanical transmission system



Jan. 13, 1931. H. c. HARRISON 1,733,519

MECHANICAL TRANSMISSION SYSTEM 7 Original Filed May 26, 1926 2 Sheets-Sheet 1 uummmgmmwmgnmumuwgumnuguyugmgug Jan. 13, 1931. H. c. HARRISON 1,738,519

MECHANICAL TRANSMISSION SYSTEM I Original Filed May 26, 1926 2 Sheets-Sheet 2 Patented Jan. 13, 1931 IIENRY G. HARRISON, F PORT WASHINGTON, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK MECHANICAL TRANSMISSION SYSTEM 7 Application filed May 26, 1926, Serial No. 111,706. Renewed June 11, 1828.

This invention relates to systems for the transmission of the mechanical vibratory energy and is a continuation in part of patent application Serial No. 603,005, filed No- 6 vember 24, 1922.

One object of this invention is to obtain a required phase shift or time delay by means ofa mechanical transmission system.

Another object of this invention is to improve the coupling between electrical and mechanical systems. a

Another object oithis invention is to efliciently couple a mechanical system to an electrical system, at the same time properly terminating the mechanical system in a de sired impedance.

As explained in U. S. Patent 1,678,116, issued July 24, 1928, which is a continuation in part of the patent application referred to above, the characteristics of wave motionare analogous in mechanical and electrical systems so that the fundamental mechanical and electrical equations are identical exceptfor the symbols employed. The corresponding quantities in the two systems are:

Mechanical systems Electrical systems Force Electromotive force Displacement Charge Velocity of vibration Current Mass Inductance Stiffness or elasticity Reciprocal of capacity Friction Resistance structure is defined as the natural logarithnr oi the vector ratio of the steady state currents at two points separated by a unit length in a uniform line of infinite length or at two successive corresponding points in a line of recurrent structure of infinite length, that where 1 is the input current and L the output current, This definition and expression also hold true for mechanical systems where I and 1 represent the mechanical currents (velocities of vibration).

The propagation constant is composed of two components (P=A+jB). The real part A is called the attenuation constant and the imaginary part B is calledthe hase constant or wave length constant. ince B is the phase or wave length constant, i. ,e., the retardation angle in radians, the velocity (V) of the propagation of a wave of angular velocity (m) is or the time of transmission or retardation (25) per unit length or per section is A feature of this invention is a mechanical system for obtaining a phase shift or time delay analogous to the electrical systems used for the same purpose. Mechanical lines either of the continuously loaded or lumped loaded types are particularly adapted for this purpose, since the delay is a direct function of the mass of the line and, by means of the loading,a large delay may be obtained with a short length of line. Mechanical networks of recurrent structure, for example wave filters analogous to the electrical wave filters disclosed and claimed in U. S. Patent No. 1,227,113 granted to G. A. Campbell May 22, 1917, are also well suited "for this purpose.

Another feature of this invention is a mechanical network for properly terminating a mechanical line or filter. This is a desirable arrangement since in order toprevent reflection losses, it is necessary that a transmission network be terminated in an impedance equal to the impedance of the network, and, as disclosed and claimed in U. S. Patent No. 1,493,600 granted to G. A. Campbell May 13, 1924, it is particularly expedient that a filter composed of a finite number of recurrent sections be terminated in an impedance equal to that of an infinite series of such sections, in

' pled to an electrical. system so that the mechanical system is terminated in an impedance equal to the impedance of the electrical system in such a way as to give the desired terminating impedance. Broadly thesame design principles set forth and the same features described and claimed in my copending patent application, Serial No. 678,935, filed December 6, 1923, in connection with an electromagnetic receiver for operating a sound radiating system, are made use of in the construction of a receiver for terminating and coupling to an electrical system a mechanical line or filter, in accordance with this feature oi the invention.

- These and other objects and features of the invention can be more readily understood by reference to the following detailed description in connection with the which: V p

' Fig. l is a side view of one embodiment of the invention for transmitting torsional mo tion; I I

Fig. 2 is an end view of the system of drawings in Fig.1; v

Figs. 3 and 4 are end views or modifications of the systemof Figs; land 2;

.Fig. 5 shows a form of the invention for transmitting longitudinal vibrations V Fig. 6 is a sectional view of the system of Fig. 5; s

F ig. 7 shows a uniform line constructed in accordance with this invention} F ig. 8 shows diagrammatically an electrical low-pass filter; v

Figs. 9 and 10 show another form of invention in combination with coupling terminating arrangements;

Fig. 11 showsa modification of the form of the invention shown in'Fig. 9,- 7

Figs. 12 and 13 show a tormof this invention similar to that shown in Figs. 9 and 10., except that the line ist-erminated by means of properl designed carbon button;

Fig. 14; shows form of this invention. embodied in a system for obtaining a delay in the transmission of electrical currents;

'Fig. '15 shows electrical circuit analothis and gous to the coupling means employed in the ill system ofFig. 14 and Fig. 16 showsa form of this invention emproducing artificial reverberation. V

Figs 1 and 2 showa mechanical system, comprising a rod '21 uniformly distributed along which are a plurality of equal weights 22. When such a system is employed for transmitting torsional vibratory energy, it is analogous to lumped loaded line in which the rod 21 representsauniiorm line loaded at regular points by means ofthe weights 22.

if the dissipation in the line is kept negligible, such a system may be designed to uni- ;cept that two rods 28 and 24 are employed instead of single rod. shows an end view of a system employing Similarly, Fig. 4

four rods 25, 26, 2'? and 28.

F igs. 5 and 6 show a system for transm1tting longitudinal vibrations by means of a plunger action. Thereis shown a casing 80. containing a plurality of spaced weights 31 "separated from each other by a'plurality of thin sheets 32 ofmaterial such as aluminum foil or paper. Plungers '33 and 34- serve to close the ends of the casr. 30 so that the 3 movement of the plunger 3.8,501' example, T

will be transmitted through theair cushioning' between the-foil sheets and theispaced weights 31- to the plunger 3% at theopposite end. Thespac'ed weights constitute the mass of the mechanical line and the air between the thin air cushioned sheets of foil, together with the spring contacts ofthe sheets, presents an elastic reactiontc motion so that the system is the mechanicalequivalent of an electrical. system comprising series masses and shunt elasticities. TheWeightsBl may be considered as representing loading coils and the elasticity between the cushioned foil sheets which lie between'the weights as corresponding to theshunt capacities. The system may be designed to have definite time delay in the same way the systems described above. H

, If the sheets little In some caseslwhere a time'dclay is. rc-

quired, it may be'inore desirable to'employ a uniform line'ratherthan one of lnmpefdfela ments; Fig. shows one device 35, which -tly into th casirigso as A to substantially prevent the escape of air,

. iductauccs may be used for this purpose. This device comprises three strips of metallic material integral with each other and placed t an angle of with respectto one an nor. This bar, when subgected, for example, to a twistlng motion, may be emp' transmission'of vibratory ener y from one end to the other. llhe arrangement or the strips permits the device be subjected to la torsional movement only. and reduces to a considerable the danger otl og the devicebend due force exerted angles to itsaxis. Such ab r form delay for all freoue tion is negligible or it it i the leakage G (effect 1, for example.

is proportioned with respect to the series reslstance R in the following manner:

Under these conditions the delay per unit length is:

where M and S represent respectively the mass and elasticity per unit length.

By designing the structures of Figs. 1, 3, 4 and 5 so that the mass of the sections of line between the weights is negligible compared to the mass of the weights, they may be made to approximate a low-pass filter analogous to the electrical filter shown in Fig. 8. Such a filter is composed of a plurality of similar sections, each comprising series inductance 36 and shunt capacity 37 equivalent, respectively, to the mass M of the weights 22 and the reciprocal of the elasticity S of the interconnecting sections of the bar 21 of Fig. Within the transmission range, the phase shift constant per section of a wave filter is,

1. 1 1 I B 2 sin Z2 where Z and Z represent respectively series and shunt impedance. For the low-pass filter of Fig. 1 this is,

for all frequencies below the cut-off,

For a filter of n sections this gives a total phase shift or a total time delay r lsin w AEE Such a system is particularly suitable for use as a delay network since, below the cutoff, the attenuation is negligible and the im pedance is substantially equal to the constant value,

As set forth in detail in Patent 1,493,600, referred to above, it is desirable that, 1n order to obtain eilicient operation, awave filter be The form of a mechanical filter 40 disclosed in these figures comprises a plurality of lumped masses 41 connected by four strips 42, 43, 44 and 45 of elastic material and mounted in a casing 39. These four strips as shown in Fig. 10 are placed in four corners of a rectangle and are so regularly and angularly spaced that their projections pass through the centers of the masses 41. Each of the Weights 41, as shown in Fig. 10, is of an irregular shape to allow them to be readily mounted in the casing 39 while permitting the strips 42, 43, 44 and 45 to be subjected to a twisting vibratoryn'iotion. "The filter" is pivot-ally supported at one end by means of a pivot member to enable it to be freely twisted in accordance with the mechanical vibratory energy of the armature of a loosely coupled magnetic receiver 56. The armature 57 of this receiver is mounted in the field of a permanent magnet 58 and surrounded by two receiver coils 59 and 60, which may be connected to an electric circuit to receive signals or other alternating current waves therefrom, and to produce corresponding w mechanical vibrations of the armature. The armature 57 is coupled by means of two members 61 and 62 to the end section of the filter 40 to impress'vibrations thereon. The

resulting vibrations in the filter are transstrips 42, 43, 44 and 45 of the filter 40 a desired amount and mounting thereon a plurality of weights 48 to form a mechanical line. A plurality of thin sheets 49 of material such as metal foil are packed between the weights 48 and the casing 39. These sheets of damping material are provided for dissipating the energy transmitted to the portions of the spring strips extending beyond the mass 14 where the carbon button is coupled to the mechanical filter and it is obvious that the amount of packing employed in the particular case will depend. upon how rapidly it is desired to dissipate this energy.

Fig. 11 shows a detail of a modification of the device in which a loosely coupled magnetic receiver 63 .is substituted for the carbon button 46, the armature 64 being attached to the coupling strip 15/ Figs. 12 and 13 show a mechanical line 65 driven by a loosely coupled magnetic receiver 66 and similar to that of Fig. 9, e cepting that the terminating impedance is of the o-btained by use of a deep chamliie'r carbon button of the type disclosed and claimed in U. Patent '1,64l8,l20, issued November 8 11.927. This in tton is art-("" by ms of an arm 67, as shox and cnnprises a front electrode d electrode oll. The electrr to f?" be of flexible material, for example, a w meshor gold plated cloth, to allow .etiolis be transmitted to the deep nainher 70 heyoruil the electrode 69, 4 it I has been found that the best quality of reproduction of mechanical "vibrations ti'ansn'u ed to the front ele-trode 68 from the mechanical line takes place when only a thin layer or". carbon is located between the electrodes. ably thedistance between the elec rodes 69 should not be greater 4C0 mils. The cross sectional area and depth of the deep carbon chamber 70 should so .designed as to give thebutton a mechanical impedance equ to the mechanicalimpe 1 of. the line 65 as measured at the end orthe leverarm 67 ,jFig. 14 shows a mechanical system termi nated in a closely coupled magnetic receiver in such' manner that the im edance of the mechanical line is'matched to the impedance electrical circuits. This arrangement been shown in connection wi h delay circuit oft-the type disclosed and claimed in U.' S. Patent 1,607 ,687 issued Ncvember23, 1926. This system comprises two line sections 71 and 72 between which it is-desired to obtain definite time delay. Currents comingin from the section 71, for example, are impressed upon, the hybrid coil 73, half going to the balancing network 7 4 and halt to the delay, circuit 7 5. The network 7& is designed to have an i .ipedance to match the impedance of the delay circuit 7 5 so that no current is impressed on the line section 72' 'l he portion of the current flowing into the circuit 7 5 is transformed, by the electromagnetic receiver 6, into mechanical vibrations which are impressed upon the mechanical delay circuit 77 transmitted therethrough to the remote end 78 where they are reflected back to the input, retransformed into electrical current by the receiver 76 andliinprcssed back upon the hybrid coil 73 where they divide'between the lines 71 an i By means ofthis arrangement a requiieddelay is obtained with a line '01? half the length that would be otherwise required. 7 V

llhe mechanical delay circuit 7 7 of this embodiment of the invention is of the type 81. Oneend of the line is connected'to the armatureot the electromagnetic receiver 76 a Jd the other end is supported'by bearing Tue receiver 76 is oi the closely couglec type, for example, as described claimed Prefer;

of the electrical and mechanical systems to prevent reflection loss and to properly terminute the mechanical systen. Connected in shunt to the windings 82 and 83 of the receiver is a condenser 85 provided to properly terminate the coupling system, as debed and claimed 111 my copendmg appllr anon Serial lilo. 678,935, filed December .6,

The equivalent electrical circuit of the mechanical-system and coupling arrangement s shown in Fig. 15, where L and 0 represent 'espectively the inductance of the windings 62 and 83 and the capacity of the condenser 85, and the rectangle M, the'couplingmetween the mechanical and electricallc-irczuits, in the portion of thediagram representing the mechanical system, the series mass M the of the armature 84;; the series elasticity S the negative elasticity of the magnetic field of the air-gap the shunt icity S the elasticity of the shattoon necting the armature and the line; theseries AL ole t elasticity S the elasticity of the armature retaining spring {not shown); and the masses M and elasticlties S the masses the weights 81 and elasticities of the con- Fi 16-shows a circuit in which both ends I V V or the mechanical delay system are coupled to electrical circu ts by eans of closely cou? pied electromagnetic receivers. Thls embodiment is shown in a'type of artificial-rover beration producing circuit disclosed and claimed in UJS. Patent 1,647,2d2, issued November' '1, 1927. 'IIere a transmitter 91 is connected to a two way-one element type {i repeater circuit 92, which is in turn connected through a'mechanical delay circuit 93 to a second two way one element type repeater circuit 94 and thence through an amplifier 95 to a reproducer 96. As explained in detail in the applicationirei'erred to above, partv of the current going from the transmitter 91 is transmitted directly toxtheldelay cir- 7 cuit- 93, but the larger part divides between the input and output circuits of the vacuum amplifier 97 The energy which flows into the output circuit is lost, but the wave flowampl-ifiecl current passes to the outputlcoil :ing into the input circuit is amplifiedan d the o transmitter 91 and the delay circuit 93, half going to each, if the impedances of 91 and 93 are balanced, which must be substantially the case in order to avoid singing. The energy of that half which passes into the transmitter circuit is dissipated while the wave'fiowing into the delay circuit goes to the repeater 94 where it is amplified and the amplified current transmitted to the output coil where it divides between the reproducer circuit and the delay circuit. The wave which flows back into the delay circuit is amplified by the repeater 92 and half the amplified current is dissipated in the transmit ter circuit while the other half passes into the delay circuit and is amplified by repeater 9 1, half of the amplified current passing back into the delay circuit to repeat the cycle while the other half flows into the reproducer circuit. This last current lags behind the original current and is of similar amplitude due to the phase shift of the delay circuit, and so appears as a first reflection. Part of the current which flows back into the line is also finally impressed upon the reproducer after having been repeated and reduced by division in the hybrid coils. Thus we have a series of currents in the reproducer 96, each one lagging behind the preceding one by a definite time and decreasing in amplitude in a logarithmic ratio until the last is inapprociable.

The delay system 93 consists of a rod 99, along which are mounted weights 100, and the ends of which are connected to the armatures of two closely coupled electromagnetic receivers 101 and 102 similar to the receiver 76 shown in Fig. 14. The windings of these receivers are connected to the line sides of the hybrid coils of the repeaters 92 and 94 respectively. The receivers may be designed in the manner explained in connection with the receiver 76 of Fig. 14 so as to properly terminate the mechanical line at each end.

It is understood that this invention is not limited to the particular embodiment shown, but may be variously modified without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

1. In combinatioma system for the trans mission of mechanical vibratory energy, comprising a plurality of sections each having mass and elasticityetfectively in series and shunt relation to the line of propagation of mechanical Wave energy, an electric circuit, and a closely coupled electromagnetic receiver for coupling said mechanical system to said electric circuit, the mechanical, electrical and magnetic characteristics of said receiver being so proportioned with respect to one another and to the constants of the me chanical system and the electric circuit that said mechanical system is terminated in an impedance substantially equal to the impedance of an infinite number of similar sections for frequencies to be transmitted.

2. In combination, a mechanical transmission line having mass and elasticity efiectively in series and shunt relation to the line of propagation of wave energy and so proportioned with respect to one another as to give said line a substantially constant impedance for a wide range of frequencies to be transmitted, means associated with said line at one end for impressing vibrations thereon, and means associated with said line at the other end for terminating said line, said means comprising a mechanical line of a plurality of sections each comprising mass and elasticity so arranged and proportioned as to give said means an impedance substantially equal to the impedance of said first line for the frequencies to be transmitted thereby.

3. A combination according to claim 2, in which the terminating means includes damping means for dissipating substantially all the energy transmitted thereto.

a. In combination a mechanical transmission line comprising a plurality of sections, eacl having mass and elasticity effectively in series and shunt relation to the line of propagation of mechanical wave energy and so proportioned with respect to one another as to give said line a substantially constant transmission characteristic for a wide range of frequencies to be transmitted, means associated with one end of said line for impressing vibrations thereon, means associated with said line at another point for receiving wave en rgy therefrom, and a terminating mechanical line associated with the other end of said line, said terminating line comprising a plurality of sections each having mass and elastic elements effectively in series and shunt relation to the line of propagation of mechanical wave energy, and so proportioned with respect to one another as to give said terminating line a mechanical impedance substan tially equal to the impedance of a line of an infinite number of sections like those com prising said first line.

5. A combination according to claim 4, in which said terminating line includes damping means associated with each of said sections for dissipating substantially all the energy impressed on said line.

In witness whereof, I hereunto subscribe my name this 22d day of May A. D. 1926.

HENRY C. HARRISON 

